fix: configure Docker client to use Unix socket

Default docker-java config resolved to localhost:2375 (TCP) inside the
container. Explicitly set docker host to unix:///var/run/docker.sock
which is volume-mounted from the host.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/main/java/net/siegeln/cameleer/saas/runtime/DockerRuntimeOrchestrator.java

@@ -32,7 +32,9 @@ public class DockerRuntimeOrchestrator implements RuntimeOrchestrator {
 
     @PostConstruct
     public void init() {
-        var config = DefaultDockerClientConfig.createDefaultConfigBuilder().build();
+        var config = DefaultDockerClientConfig.createDefaultConfigBuilder()
+                .withDockerHost("unix:///var/run/docker.sock")
+                .build();
         var httpClient = new ApacheDockerHttpClient.Builder()
                 .dockerHost(config.getDockerHost())
                 .build();